Fire retardant formulations

ABSTRACT

A fire-retardant formulation for styrene-containing polymers comprising tris(2,4,6-tribromophenoxy)-s-triazine (FR-245), antimony trioxide and polytetrafluoroethylene (PTFE), wherein the bromine concentration in said fire-retardant formulation is from about 9.0 to about 10.5 wt. %, said antimony trioxide concentration being lower than about 3.2 wt. %.

FIELD OF THE INVENTION

The present invention relates to improved fire-retardant formulations.More specifically, the present invention relates to improvedfire-retardant formulations for styrene polymers and more particularlyfor High Impact Polystyrene (HIPS) and Acrylonitrile-Butadiene-Styreneterpolymer (ABS).

BACKGROUND

Styrenic resins are widely used in many applications including thosewhere fireproof materials are necessary. Such applications include forexample TV cabinets, in which there is a need for the incorporation offire-retardants (FR) in styrene-polymeric materials.

Traditional FRs for these applications include, inter cilia,decabromodiphenyl oxide and more recentlytris(2,4,6-tribromophenoxy)-s-triazine the latter known as FR-245. Theadvantages of FR-245 are good balance of properties, high level ofmechanical properties, high processing heat stability, good lightstability, high melt flow and no blooming. However, unlike formulationsbased on decabromodiphenyl oxide, the formulations based on FR-245 tendto induce long after glow time. This effect is enhanced when carbonblack is added to the formulation.

JP 11323064 discloses the incorporation of fire-retardant formulationcomprising tris(2,4,6-tribromophenoxy)-s-triazine known as FR-245,tris(3-bromo-2,2(bromomethyl)propyl)phosphate known as FR-370, antimonytrioxide (Sb203) and PTFE (polytetrafluoroethylene) in rubber reinforcedpolystyrene also known as HIPS, wherein the bromine content, the maincomponent responsible for fire retardation, is between 9.5 and 11 wt. %and wherein antimony trioxide, serving as a synergist, is between 3.5and 3.7 wt. %.

This formulation is claimed to successfully meet the requirement ofUL-94 class V-0 according to the flammability tests, where fivespecimens are ignited, twice each, and the fulfillment of 5 requirementsis necessary to pass a UL-94 V-0 standard, namely:

1. Maximum after flame time≦10 seconds (for each ignition).2. Total after flame time of 10 ignitions less or equal to 50 seconds.3. Maximum after flame+after glow time less or equal to 30 seconds.4. None of the test specimens burns or glows up to the holding clamp.5. No cotton ignition by dripping.

UL-94V is UL (Underwriter Laboratories) Standard for Safety for Testsfor Parts in Devices and Appliances.

A fire-retardant formulation containing FR-245 with 11.5 wt. % Br, 0.08wt. % PTFE and 3.5 wt. % antimony trioxide is also rated UL-94 V-0, butreducing the bromine content to 10.5 wt. % Br results in derating toUL-94 V-1 because of long afterglow time. JP 11323064 overcomes thisproblem by introducing FR-370 to the formulation, which effectivelyreduces that time, while keeping relatively low levels of bromine-basedfire-retardant.

Although JP 11323064 states that incorporation of FR-370 in theformulation allows maintaining low levels of bromine, which enhancestechnical properties of articles incorporating it and leads tocost-effective FR formulations, the inventors of the present inventionnote that FR-370 is a very expensive material and its use infire-retardant formulations offers a high-cost non-economical solutionfor reducing or eliminating the afterglow phenomenon and for achievingV-0 flammability test rating.

SUMMARY OF THE INVENTION

The applicants have surprisingly found that by lowering theconcentration levels of antimony trioxide to certain ranges whilemaintaining low levels of bromine, a fire-retardant formulation thatessentially meets the requirement UL-94 class V-0 standards is achievedwithout evoking the need for high-cost or other materials. Inparticular, it has also been found that even when incorporatingadditives to the formulation as carbon black pigment those concentrationranges of the respective components still allow to successfully pass thestandard flammability tests.

It is therefore an object of the present invention to provide afire-retardant formulation that essentially meets the requirementstandard according to the flammability tests.

It is yet another object of the present invention to provide a pigmentedfire-retardant formulation that essentially meets the requirementstandard according to the flammability tests.

Still another object of the present invention is to provide afire-retardant formulation with improved technical and mechanicalproperties.

Still another object of the present invention is to provide afire-retardant formulation that is cost-effective.

Still another object of the present invention is to provide afire-retarded styrene-containing polymer for injection molding orextrusion essentially comprising said fire-retardant formulation.

Still another object of the present invention is to providefire-retarded styrene-containing polymer that may be HIPS or ABS.

This and other objects of the invention will become apparent as thedescription proceeds.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a fire-retardant formulation that meetsthe requirement UL-94 V-0 standard according to the flammability testsand which is also cost-effective.

According to the present invention the formulation comprises FR-245,antimony trioxide, PTFE and optionally carbon black pigment, in whichthe acceptable concentrations of bromine range between about 9.0 andabout 10.5 wt. % and those of antimony trioxide range between about 1.8and about 3.2 wt. %.

Styrene rubber reinforced polymers containing fire-retardantformulations (FR-HIPS) are often required to possess a black or graycolor. This is achieved by the incorporation of carbon black, apreferred pigment, to these formulations. However, a side-effect ofcarbon black when introduced in a fire-retardant formulation is longperiod of time afterglow effect, where the formulation comprisesessentially the same components having the same concentrations asdisclosed in JP 11323064, excluding the presence of FR-370.

In addition to the polystyrenic polymer, halogen based fire retardant,antimony oxide, PTFE and the carbon black, there can be present in theformulation conventional additives in their conventional amounts.Examples of such additives are: fillers, pigments, dyes, impactmodifiers, UV stabilizers, antioxidants, processing aids, nucleatingagents, lubricants and the like.

The flame retarded formulations may be shaped into the final object byprocesses that are well known to the person skilled in the art; nonlimiting examples of such processes are: injection molding, extrusion,press molding, vacuum forming, etc.

EXAMPLES

The present invention will now be described in more detail with Examplesand Reference Examples.

Tables 1-3 below summarize the materials used for the preparation of thetest samples as well as the methods and conditions for theirpreparation. Flammability was tested according to UL-94V.

TABLE 1 Materials TRADE NAME GENERAL INFO HIPS Styron 472 ex DowChemical ABS Magnum 3404 ex Dow Chemical Antimony trioxide ACC-BS exAntraco FR-245 ex DSBG Tris(2,4,6-tribromophenoxy)-s- triazine F-3020 exDSBG Endcapped brominated epoxy oligomer (MW 2,000) FR-1210 ex DSBGDecabromodiphenyl oxide Carbon Black PSB 183 ex Hubron manufacturingdivision limited PTFE Hostaflon 2071 ex Dynon-fine powder (500μ)Antimony trioxide is added as 80% concentrate in polystyrene carrier.Carbon black is added as 35% concentrate in polystyrene carrier.

Compounding

All formulations were prepared under the same conditions.

The components are weighed on Sartorius semi-analytical scales withconsequent manual mixing in plastic bags, All the components areintroduced into an extruder via K-SFS 24 gravimetric feeding system ex.K-Tron.

Compounding is performed in a co-rotating twin-screw extruder ZE25 exBerstorff with L/D=32. The compounding conditions are presented in Table2. The extruded strands are pelletized in pelletizer 750/3 ex AccrapakSystems Limited.

The obtained pellets are dried in a circulating air oven ex HeraeusInstruments at 75° C. for 4 hours.

TABLE 2 Compounding conditions PARAMETER UNITS Set values Feeding zonetemperature (T₁) ° C. no heating T₂ ° C. 160 T₃ ° C. 230 T₄ ° C. 230 T₅° C. 230 T₆ ° C. 230 T₇ ° C. 200 T₈ ° C. 230 T₉ ° C. 230 Temperature ofmelt ° C. 230 Screw speed RPM 300

Injection Molding

Test specimens were prepared by injection molding in an Allrounder 500150 ex. Arburg. All test specimens were prepared under the sameconditions. The injection molding conditions are presented in Table 3.

TABLE 3 Injection molding conditions PARAMETER UNITS Set values T₁(Feeding zone) ° C. 180 T₂ ° C. 200 T₃ ° C. 230 T₄ ° C. 230 T₅ (nozzle)° C. 230 Mold temperature ° C. 40 Injection pressure bar 500 Holdingpressure bar 250 Back pressure bar 20 Injection time sec 0.1 Holdingtime sec 10.0 Cooling time sec 5.0 Mold closing force kN 500 Fillingvolume (portion) ccm 21 Injection speed ccm/sec 10

Conditioning

Prior to UL-94 testing test specimens are conditioned at 70° C. for 168hours and at 23° C. for 168 hours.

Compositions and flammability test results are presented in Table 4 forHIPS compositions and in Table 5 for ABS compositions.

TABLE 4 HIPS compositions and flammability test results ReferenceReference Reference Reference Reference Reference Reference ReferenceReference Components Units Example 1 example 2 example 3 example 4example 5 example 6 example 7 example 8 example 9 HIPS Styron 472 % 82.581.5 84.4 84.5 83.4 79.2 78.2 81.5 81.6 FR-245 % 17.2 17.2 14.9 14.9FR-1210 % 13.9 13.9 12.0 12.0 12.0 F-3020 % Antimony trioxide % 3.5 3.53.5 3.5 3.5 3.5 3.5 3.5 3.5 PTFE Hostaflon 2071 % 0.1 0.1 0.1 0.1 0.10.1 0.1 Carbon Black % 1.0 1 1.0 Bromine calculated % 11.5 11.5 10 10 1011.5 11.5 10 10 Flammability UL-94V at 1.6 mm Max flaming time sec 2 1 24 1 2 1 2 3 Total flaming time sec 10 9 10 17 10 11 7 12 11 Max afterglow time sec 12 0 0 0 11 20 36 31 0 Max after glow + sec 13 1 1 1 12 2236 31 1 after flame time Specimens dripped num 0 0 0 3 0 0 0 0 5 Cottonignition num 0 0 0 2 0 0 0 0 5 Sample burned up to num 0 0 0 0 0 0 0 0 0the holding clamps Rating V-0 V-0 V-0 V-2 V-0 V-0 V-1 V-1 V-2 HIPScompositions and test flammability results Reference Reference ReferenceReference Reference Reference example example example example exampleexample Components Units 10 11 12 13 14 15 Example 1 Example 2 Example 3HIPS Styron 472 % 80.5 80.8 83.0 81.6 81.2 79.6 81.0 81.5 80.6 FR-245 %14.9 14.9 14.9 14.9 14-9 10.4 14.9 14.9 10.4 FR-1210 % F-3020 % 5.4 5.4Antimony trioxide % 3.5 3.2 1.0 2.5 2.5 3.5 3.0 2.5 2.5 PTFE Hostaflon2071 % 0.1 0.1 0.1 0.02 0.4 0.1 0.1 0.1 0.1 Carbon Black % 1 1.0 1.0 1.01.0 1.0 1.0 1.0 1.0 Bromine calculated % 10 10 10 10 10 10 10 10 10Flammability UL-94V at 1.6 mm Max flaming time sec 1 3 78 6 1 3 2 7 4Total flaming time sec 9 13 338 26 7 12 12 16 18 Max after glow time sec54 35 0 31 45 35 21 2 22 Max after glow + sec 55 37 78 33 46 38 22 2 24after flame time Specimens dripped num 0 0 3 0 0 0 0 0 Cotton ignitionnum 0 0 3 0 0 0 0 0 Sample burned up to num 0 0 4 0 0 0 0 0 0 theholding clamps Rating V-1 V-1 HB V-2 V-1 V-1 V-0 V-0 V-0

Table 4 above summarizes several composition and flammability testresults of prior art related fire-retardant formulations as well as offormulations relating to the present invention. From this table it isclearly seen that:

-   (a) Formulations (Reference Example-6) based on JP 11323064 pass    successfully the V-0 flammability test, but introducing 1 wt. %    carbon black pigment (Reference Example-7), results in derating to    V-1 due to long afterglow time.-   (b) In fire-retardant FR-1210 (decabromodiphenyl oxide) based    formulations—Reference Examples 1-5—the first two formulations    substantially having the same bromine, antimony trioxide and PTFE    concentrations as in Reference Examples 6 and 7 pass V-0 tests, even    when containing carbon black pigment (Reference Example 2). Reducing    bromine content to 10 wt. % and then further elimination of PTFE    from this formulation result in V-0 and V-2 rating, respectively    (Reference Example 3 and Reference Example 4), the latter is due to    burning drops ignited cotton effect. Addition of carbon black to    Reference Example 3 does not derate the formulation and it passes    V-0 tests (Reference Example 5). It should be noted that the    antimony trioxide remains essentially unchanged in all those    formulation variations.-   (c) Reference Example 8, Reference Example 9, Reference Example 10    and Example 2 to Example 3 relate to FR-245 containing formulations    having varying concentrations of the components Further reduction of    FR-245 to 10 wt. % bromine while keeping the antimony trioxide    concentration relatively high (Reference Example 8) results in    derating to V-1. Omission of PTFE from this formulation (Reference    Example 9) results in dripping with cotton ignition and V-2 rating.    Further addition of carbon black to Reference Example 8 (Reference    Example 10) results in long afterglow effect and a rating of V-1.    However, reduction of antimony trioxide to 2.5 wt. % (Example 2)    surprisingly improves flammability retardation and is rated V-0.    Further reduction of antimony trioxide to 1 wt. % (Reference    Example 12) results in total burning of the specimen up to the    clamps and in a HB rating. The upper concentration limit of antimony    trioxide is tested in Reference Example 11 vs. Example 1; at    antimony trioxide concentration of 3.2 wt. % the formulation is    rated V-1 because of long after glow time (Reference Example 11); at    antimony trioxide concentration of 3.0 wt. % the formulation is    rated V-0 (Example 1). The concentration limits of PTFE are tested    in formulations Reference Example 13, 0.02 wt. %, and Reference    Example 14, 0.4 wt. %. In the first an effect of burning drops    ignited cotton leads to V-2 rating. The second is rated V-1 due to    long afterglow time.-   (d) The employment of both FR-245 and F-3020 (MBEO endcapped    brominated epoxy resin) as the bromine fire-retardants, the first    contributing about 7 wt. % and the second about 3 wt. % of the    bromine content, leads to long afterglow time (Reference Example 15)    when incorporating 3.5 wt. % antimony trioxide, i.e. V-1 rating, and    to successful results (Example 3) when lowering antimony trioxide    concentration to 2.5 wt. %, i.e. V-0. These two results are similar    to the ones achieved for formulations containing only FR-245, i.e.    Reference Example 10 and Example 2, and further stress the optimal    relation between bromine fire-retardant and antimony trioxide    synergist contents.

TABLE 5 ABS compositions and results of flammability results ReferenceComponents Units example 16 Example 4 ABS Magnum 3404 % 80.0 81.0 FR-245% 14.9 14.9 Antimony trioxide % 4.0 3.0 PTFE Hostaflon 2071 % 0.1 0.1Carbon Black % 1.0 1.0 Bromine calculated % 10 10 Flammability UL-94V at1.6 mm Max flaming time Sec 5 7 Total flaming time Sec 16 29 Max afterglow time Sec 36 21 Max after glow + after Sec 38 23 flame timeSpecimens dripped Num 0 0 Cotton ignition Num 0 0 Sample burned up tothe Num 0 0 holding clamps Rating V-1 V-0

Table 5 demonstrates that the same effects, which are observed in HIPSformulations, are also applied in ABS based formulations.

HIPS and ABS containing fire-retardant formulations containing FR-245 ora combination of FR-245 and BEO's at low bromine content and with theincorporation of carbon black do not pass UL-94 V-0 because of longafter glow time. It is surprisingly found that at low antimony trioxideconcentrations it is possible to pass UL-94 V-0 and get economiccost-effective formulations with good mechanical, thermal and processingproperties.

While examples of the invention have been described for purposes ofillustration, it will be apparent that many modifications, variationsand adaptations can be carried out by persons skilled in the art,without exceeding the scope of the claims.

1-12. (canceled)
 13. A fire-retarded styrene-containing polymer comprising fire-retardant formulation for injection-molding or extrusion, wherein said fire-retardant formulation comprises tris(2,4,6-tribromophenoxy)-s-triazine (FR-245), antimony trioxide and polytetrafluoroethylene (PTFE) and optionally carbon black, wherein the bromine concentration in said fire-retardant formulation is from about 9.0 to about 10.5 wt. % and the antimony trioxide concentration is equal to or less than 3.0 wt. %, while excluding tris(tribromoneopentyl)phosphate (FR-70) from said formulation.
 14. The fire-retarded styrene-containing polymer of claim 13, wherein the antimony trioxide concentration is from 1.8 to 3.0 wt. % and the PTFE concentration is from about 0.03 to 0.2 wt. %.
 15. The fire-retarded styrene-containing polymer of claim 14, wherein the fire-retardant formulation further comprises a brominated epoxy resin (BEO) or an endcapped brominated expoxy resin (MBEO).
 16. The fire-retarded styrene-containing polymer of claim 15, wherein the bromine concentration of said BEO or MBEO is about 3 wt. %.
 17. A fire-retarded styrene-containing polymer according to claim 13, wherein the carbon black concentration is from 0.3 to 2 wt. %.
 18. A fire-retarded styrene-containing polymer according to claim 13, said polymer comprising a fire-retardant formulation for injection-molding or extrusion, said formulation comprising bromine in a concentration of about 10 wt. % essentially comprised in tris(2,4,6-tribromophenoxy)-s-triazine (FR-245), antimony trioxide in a concentration of 3.0 wt. %, PTFE in a concentration of about 0.1 wt. % and carbon black in a concentration of about 1.0 wt. %.
 19. A fire-retarded styrene-containing polymer according to claim 13, said polymer comprising a fire-retardant formulation for injection-molding or extrusion, said formulation comprising bromine in a concentration of about 10 wt, % essentially comprised in tris(2,4,6-tribromophenoxy)-s-triazine (FR-245), antimony trioxide in a concentration of about 2.5 wt. %, PTFE in a concentration of about 0.1 wt. % and carbon black in a concentration of about 1.0 wt. %.
 20. A fire-retarded styrene-containing polymer according to claim 13, said polymer comprising a fire-retardant formulation for injection-molding or extrusion, said formulation comprising bromine in a concentration of about 10 wt. % essentially comprised in tris(2,4,6-tribromophenoxy)-s-triazine (FR-245) and BEO, antimony trioxide in a concentration of about 2.5 wt. %, PTFE in a concentration of about 0.1 wt. % and carbon black in a concentration of about 1.0 wt. %.
 21. A fire-retarded styrene-containing polymer according to claim 13, wherein said polymer is high-impact polystyrene (HIPS).
 22. A fire-retarded styrene-containing polymer according to claim 13, wherein said polymer is acrylonitrile-butadiene-styrene polymer (ABS).
 23. A method for fire retarding a styrene-containing polymer, said method comprising incorporating into said polymer a fire-retardant formulation comprising tris(2,4,6-tribromophenoxy)-s-triazine (FR-245), antimony trioxide to a concentration equal to or less than 3.0 wt %, polytetrafluoroethylene (PTFE), optionally carbon black and optionally a brominated epoxy resin (BEO) or an endcapped brominated epoxy resin (MBEO), while excluding tris(tribromoneopentyl)phosphate (FR-70) from said formulation.
 24. A method according to claim 23, wherein the bromine concentration in the fire-retardant formulation is from 9.0 to 10.5 wt. %, the antimony trioxide concentration is from 1.8 to 3.0 wt. % and the PTFE concentration is from about 0.03 to 0.2 wt. %.
 25. The method according to claim 23, wherein the bromine concentration from the BED or MBEO is about 3 wt. %.
 26. The method according to claim 23, wherein the styrene-containing polymer is HIPS.
 27. The method according to claim 23, wherein the styrene-containing polymer is ABS. 